Depends on how warped it is. I've been succesful at times by not touching the tip or near the tip and just doing the back portion if it's only slightly warped. I've also found lowering the ligature on the reed and making it very tight sometimes solves the problem at the time, again if it's only slightly warped. That's worked for me at times on my bass reeds. My clarinet reeds have almost never warped because of the way I did humidity control over most of my long playing career once I learned how to do it. See my website if you're interested.